Positioning linkage for rotatably mounted upper guard of portable power-driven saw



July 26, 1966 D. E. ELSON 3,262,473

POSITIONING LINKAGE FOR ROTATABLY MOUNTED UPPER GUARD OF PORTABLE POWER-DRIVEN SAW Filed May 11, 1964 INVENTOR DONALD E. ELSON ATTORNEY United States Patent() POSITINING LINKAGE FR ROTA'I'ABLY MUNTED UPPER GUARD F PRTABLE PWER-DRIVEN SAW Donald E. Elson, Baltimore, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Filed May 11, 1964, Ser. No. 366,343 4 Claims. (Cl. 143-43) The present invention relates to a positioning linkage means for a rotatably-mounted upper guard of a portable power-driven rotary saw, and more particularly to a linkage means for automatically pivoting the rotatablymounted upper guard in response to the selective raising and. lowering movements of the lhousing structure with respect to the planar shoe plate, such that the front portion of the circular saw blade is substantially covered at all times, and such that the distance between the lower front portion of the guard and the shoe plate remains at a substantially constant level.

In the prior art of which I am aware, as for example, that which is exempliiied in the now-expired Wallace et al. patent 1,792,204, the blade guard is rotatably mounted upon the hub portion of the housing structure; and the lower front portion of the guard is forked, providing in effect a ca m slot, which receives a stationary pivot pin mounted between respective ears carried on the shoe plate. As the housing structure is raised or lowered with respect to the shoe plate, the rotatably-mounted guard is constrained by the pivot pin which is guided within the cam slot on the guard; and thus the guard pivots on the hub, that is, the guard rotates through an angle, such that the front portion of the saw blade is protected at all times by the guard in the various adjusted positions of the housing with respect to the shoe'plate.

This prior art structure, however, is not entirely satisfactory and suffers from a number of annoying deficiencies. First, the rotatably-mounted blade guard with the cam slot formed therein may not slide freely over the stationary pivot pin, :but rather may tend to hang up, a condition that may .be experienced should the cam slot have one or more burrs formed therein during its machining operation, or else, become clogged by gum and saw dust particles. Secondly, the particular formation of the cam slot on the guard usually involves a milling operation or its equivalent, and this is usually awkward and time consuming and hence expensive, Thirdly, a certain degree of sliding clearance will be required between the pin and its cam slot; and if it is desired to mount the depth calibration scale conveniently on the rotatably-mounted guard, the clearance between the pin and its slot will generate an inherent inaccuracy, a condition which will become even more pronounced with wear during the life of the tool.

Accordingly, it is an object of the present invention to alleviate the deiiciencies of the prior art by providing a positioning linkage means for the rotatably-mounted upper guard of a portable power-driven saw.

It is another object of the present invention to provide a linkage means including a pivoted lever having an inherent mechanical advantage for facilitating a quick and easy pivoting movement of the guard in response to the selective raising and lowering movement of the housing structure with respect -to the shoe plate.

It is yet another object of the present invention to provide a pivoted lever located substantially within the hollow rotatably-mounted guard, such that the lever does not obscure or otherwise impair .the operators line-of-cut and blade visibility, nor interfere with the design symmetry and appearance of the overall tool.

It is a further object of the present invention to pro- ZYB Patented July 26, 1956 ICC vide a linkage means having a relatively high degree of precision, thereby maintaining accuracy should the depth calibration scale be formed as part of the rotatablymounted guard.

It is a still further object of the present invention to provide a linkage means having a rugged and reliable structure, yet one which may be manufactured easily and economically.

The present invention finds particular utility in conjunction with a portable power-driven saw of the type having a shoe plate, a saw blade extending beyond the shoe plate, `a housing on the shoe plate with a motor connected to drive the blade, an adjustable means to raise and lower the housing with respect to the shoe plate for selective depths of cut, and an upper blade guard rotatably mounted on the housing.

The present invention comprises an improved positioning linkage means for the rotatably-mounted upper guard, such that the guard automatically pivots in response to the selective raising and lowering of the housing with respect to the shoe plate, thereby maintaining the front of the saw blade (above the shoe plate) substantially-covered at all times.

The improved means includes a link having a pair of ends, and means are provided to pivotably mount one end of the link to the rotatably-mounted upper guard. Means are further provided for mounting the other end ot' the link for movement in response to the selective raising and lowering movement of the housing with respect to the shoe plate; and the result is such that, whenever the housing is raised with respect to the shoe plate, the guard rotates through an angle in a direction towards the forward end of the shoe plate, thereby maintaining the front of the saw blade substantially covered at all times.

In accordance with the specific teachings of the present invention, the improved linkage means includes a link which is positioned substantially within the lower forward portion of `the substantially-hollow upper guard. The link is formed with respective upper and lower ends. Means are provided to pivotably mount the lower end of the link to a depth control member, the latter being part of the depth-of-cut adjustment means for selectively raising and lowering the housing structure with respect to the shoe plate; and means are further provided to pivotably mount the upper end of the link lto the rotatably-mounted upper guard. Consequently, whenever the housing is raised with respect to the shoe plate, the guard rotates through an angle in a direction towards the forward end of the shoe plate, thereby maintaining the front of the saw blade substantially covered at all times.

In a preferred embodiment, the link is bifurcated and comprises a pair of legs, each of which terminates in a respective one of the ends. These legs are bent approximately at a right angle -to one another and diverge from one another in a direction towards the shoe plate. Covnsequently, the link is maintained substantially within the guard at all times and does not obscure or otherwise impair the operators line-of-cut and blade visibility in the various adjusted positions of the housing and guard with respect to the shoe plate.

These and other objects of the present invention will become apparent from a reading of the following speeltication, 4taken in conjunction with the enclosed drawings, in which:

FIGURE l is a si-de elevation of a typical portable power-driven saw, the unit being in its maximum depth of cut position, and part of the saw blade and its upper guard being broken alway to illustrate the pivoted link of the present invention;

FIGURE 2 is a view corresponding to that of FIGURE 1, but showing the housing structure of the saw unit raised with respect to the shoe plate to provide a lesser depth of cut, and further showing the manner in which the pivoted link swings through an angle to cause the rotatably-mounted upper guard to rock in a direction forwardly of the shoe plate so as to maintain the -front of the saw blade (above the shoe plate) substantially protected;

FIGURE 3 is a section view taken along the lines 3-3 `of FIGURE l, showing the means for rotatably mounting the upper guard upon the h-ub portion of the housing Structure;

FIGURE 4 is an enlarged fragmentary view of FIG- URE 3, showing a preferred embodiment of the pivoted link, and further showing in broken lines the alterna-te positions of the pivoted link and rotatably-mounted upper guard;

FIGURE 5 is a transverse section View taken along the lines 55 of FIGURE 4, showing the means `for pivotably mounting the link to the inner wall of the rotatablymounted upper guard; FIGURE 6 is a transverse section view taken along the lines 6-6of FIGURE 4, enlarged over the scale of FIG- URE 4, and showing the means for pivotably mounting the opposite end of the link to a laterally-extending ear formed integrally with the base portion of a depth control member;

FIGURE 7 is a detail perspective view of a preferred embodiment of the pivoted link;

FIGURE 8 is a partial perspective view looking from the rear side portion of the shoe plate, showing a preferred means for pivotably mounting the lower end of the link to the laterally-extending ear of the depth control mem-ber, the latter preferably being mounted pivotably on the shoe plate; and

FIGURE 9 is a modification illustrating the manner in which the pivoted linkage may be connected directly to the shoe plate by means of a ball-type joint which permits swiveling of the link in two-mutually perpendicular planes, one of which is compatible with a depth adjustment of the saw blade, and the other a bevel adjustment.

With reference to FIGURES 1, 2, and 3, there is illustrated a portable electric saw 10 with which the teachings of the present invention may find particular utility. It will be appreciated by those skilled in the art, however, that the teachings of the present invention -are equally applicable to a variety of related power-driven rotary tools of a similar design and purpose. With this in mind, Athe overall saw 10 comprises a substantially-hat shoe plate 11 by means of which the saw unit may be supported upon the top surface of a workpiece, a saw blade 12 extending beyond the shoe plate to'engage the work, a housing structure 13 mounted on the shoe plate and provided with a motor (not shown) having an arbor 14 to drive the blade, the blade being mounted on the arbor by means of a lock nut 14a, an upper control handle 15 mounted on the housing structure and having a trigger switch 16 for energizing the unit from a line cord 17, a front knob 18 to assist in handling and guiding the overall saw unit, an auxiliary outbard shoe plate 19 secured to the shoe plate 111 by means of clamp screws 20, an upper blade guard 21, a pivoted lower blade guard 22 adapted to telescope within the upper guard upon engagement with the work, and a lever 23 carried by the lower guard for facilitating its optional manual retraction within the upper guard.

With particular reference to FIGURE 3, the upper blade guard 21 is substantially hollow and is rotatably mounted upon the hub portion 24 of the housing structure 13. Also, the hub 24 is provided with a pair of guard bushings 25 and 26 for a rotatable mounting of the lower guard upon the hub.

The positioning linkage means of the present invention comprises a pivoted link 27, shown inperspective' vview in FIGURE 7. This link 27 is preferably provided with a pair of leg portions 28 and 29 which terminate in respective end portions 30 and 31. The end portion 31 lof the upper leg 29 is pivotably mounted to the inside wall, see FIGURE 5, off the rotatably-mounted upper guard by means of a headed screw 32 which passes through the opening 31a of the link and is received within a tapped bore 33 of a boss 34 formed on the inner wall of the guard. The opposite end 30 of the link, see FIG- URE 6, is pivotably mounted to a laterally-extending ear 35 (of a depth control member 36) by means of a headed screw 37 which passes through the opening 31a in the link and is received within a tapped bore 33 of a boss 39 formed on the end of the respective ear 35. Preferably, but not necessarily, this respective ear 35, see FIGURE 8, is pivotably mounted on a pin 40 which is A journaled in a bracket member 41 mounted directly to the shoe plate 11. Y In suchl a manner, and as shown more particularly in FIGURE 4, whenever the housing structure 13 is raised or lowered with respect to the shoe plate 11, the pivoted link 27 will rotate through an angle (counterclockwise as shown in FIGURE 4) and will thereby cause the rotatably-mounted upper guard 21 to have a conjoint pivoted movement (clockwise as viewed in FIGURE 4) with the result that the distance between the shoe plate 11 and the lower front portion 42 of the guard will be maintained substantially constant, thereby maintaining the front exposed portion of the saw blade (between the shoe plate and the guard) substantially protected at all times.

In the preferred embodiment, the respective legs 28 and 29 of the pivoted link 27 are formed approximately at a right angle to'one another, diverge away from each other in a direction towards the shoe plate, see FIGURES 4 and 7, with the result that the link 27 is maintained substantially within the guard 21 and hence does not obscure or impair with the operators line-of-cut and blade visibility, nor interefere with the design appearance of the tool.

A modification of the present invention is illustrated in FIGURE 9. Here, the modified link 27 is connected directly to the shoe plate 111 by means of a ball-type connection comprising a spherical knuckle 43 formed on the lower end of the link 27. The knuckle 43 is retained in a bracket 44 secured on the shoev plate and has a spherical sea-t 45 to journal the knuckle.

The depth control member 36 and the means to pivotably mount it to the shoe plate 11 forms no part of the present invention, but is described in detail in the copending McCarty et al. application Ser. No. 366,070, tiled May 8, 1964, entitled Depth and Bevel Adjustment `Means for Portable Power-Driven Saw and assigned to the assignee of the present invention.

Obviously, many modifications may be made4 without departing from the basic spirit of the present invention; and accordingly, within the scope of the appended claims, the invention may be practiced other than has ybeen specifically described herein.

I claim:

1. In a portable power-driven saw of the type having a shoe plate, a saw blade extending beyond the shoe plate, a housing on the shoe plate with a motor connected to drive the blade, adjustable means to raise and lower the housing with respect to the shoe plate for selective depths of cut, and a substantially-hollow upper blade guard rotatably mounted upon the housing, the improvement which comprises:

(a) a link having a pair of ends; said link being positioned substantially within the lower forward portion of the guard;

(b) means to pivotably mount one end of said link to the rotatably-mounted upper guard; and

(c) means mounting the other end of said link in relation to the shoe Iplate for movement of said link in response to selective raising and lowering movements of the housing with respect to the shoe plate,I

whereby whenever the housing is raised with respect to .the shoe plate, the guard rotates through an angle in a direction towards the forward end of the shoe plate, thereby maintaining the front of the saw blade substantially covered at all times.

5 lower the housing with respect to the shoe plate forv 2. In a portable power-driven saw of the type having a shoe plate, a saw blade extending beyond the shoe plate, a housing on the shoe plate with a motor connected to drive the blade, means including a depth control member adjustably secured to the housing to raise and -lower the housing with respect to the shoe plate for selective depths of cut, and a substantially-hollow upper blade guard .rotatably mounted upon the housing, the improvement which comprises:

(a) a link positioned substantially within the lower forward portion' of the guard;

(b) said link having respective upper and lower ends;

(c) means to pivotably mount said lower end of said link to the depth control member; and

(d) means to pivotably mount said upper end of said link to the rotatably-mounted upper guard, where by whenever the housing is raised with respect to the shoe plate, the guard rotates through an angle in a direction towards the forward end of the shoe plate, thereby maintaining the front of the saw blade substantially covered at all times.

3. The improvement of claim 2, wherein:

(a) said link comprises a pair of legs, each of which terminates in a respective one of said ends; and wherein:

(b) said -legs of said link are bent approximately at a right angle to one another and diverge from one selective depths of cut, said adjustable means including a depth control member having a laterally-extending ear, and an upper blade guard rotatably mounted upon the housing, the improvement which comprises:

10 (a) a link having a pair of ends;

(b) means to pivotably mount one end of said link to the rotatably-mounted upper guard; and

(c) means mounting the other end of said link for movement of said link in response to selective raising and lowering movements of the housing with respect to the shoe plate, whereby whenever the housing is raised with respect to the shoe plate, the guard rotates through an angle in a direction towards the forward end of the shoe plate, thereby maintaining the front of the saw blade substantially covered at all time;

(d) said last-named mounting means comprising means to pivotably mount said other end of said link to said ear of said depth control member.

References Cited by the Examiner UNITED STATES PATENTS 2/1951 Briskin.

FOREIGN PATENTS another in a direction towards the shoe plate, whereby said link is maintained substantially within the guard and does not obscure the operators line-ofcut and blade visibility in the various adjusted positions of the housing with respect to the shoe plate.

137,729 lO/1952` Sweden.

WILLIAM W. DYER, JR., Primary Examiner.

W. D. BRAY, Assistant Eaj-azrniner 

1. IN A PORTABLE POWER-DRIVEN SAW OF THE TYPE HAVING A SHOE PLATE, A SAW BLADE EXTENDING BEYOND THE SHOE PLATE, A HOUSING ON THE SHOE PLATE WITH A MOTOR CONNECTED TO DRIVE THE BLADE, ADJUSTABLE MEANS TO RAISE AND LOWER THE HOUSING WITH RESPECT TO THE SHOE PLATE FOR SELECTIVE DEPTHS OF CUT, AND A SUBSTANTIALLY-HOLLOW UPPER BLADE GUARD ROTATABLY MOUNTED UPON THE HOUSING, THE IMPROVEMENT WHICH COMPRISES: (A) A LINK HAVING A PAIR OF ENDS; SAID LINK BEING POSITIONED SUBSTANTIALLY WITHIN THE LOWER FORWARD PORTION OF THE GUARD; (B) MEANS TO PIVOTABLY MOUNTED ONE END OF SAID LINK TO THE ROTATABLY-MOUNTED UPPER GUARD; AND (C) MEANS MOUNTING THE OTHER END OF SAID LINK IN RELATION TO THE SHOE PLATE FOR MOVEMENT OF SAID LINK IN RESPONSE TO SELECTIVE RAISING AND LOWERING MOVEMENTS OF THE HOUSING WITH RESPECT TO THE SHOE PLATE, WHEREBY WHENEVER THE HOUSING IS RAISED WITH RESPECT TO THE SHOE PLATE, THE GUARD ROTATES THROUGH AN ANGLE IN A DIRECTION TOWARDS THE FORWARD END OF THE SHOE PLATE, THEREBY MAINTAINING THE FRONT OF THE SAW BLADE SUBSTANTIALLY COVERED AT ALL TIMES. 